Krisela Steyn

Lipids, lipoproteins, and apolipoproteins as risk markers of myocardial infarction in 52 countries (the INTERHEART study): a case-control study

BACKGROUND Whether lipoproteins are better markers than lipids and lipoproteins for coronary heart disease is widely debated. Our aim was to compare the apolipoproteins and cholesterol as indices for risk of acute myocardial infarction. METHODS We did a large, standardised case-control study of acute myocardial infarction in 12,461 cases and 14,637 age-matched (plus or minus 5 years) and sex-matched controls in 52 countries. Non-fasting blood samples were available from 9345 cases and 12,120 controls. Concentrations of plasma lipids, lipoproteins, and apolipoproteins were measured, and cholesterol and apolipoprotein ratios were calculated. Odds ratios (OR) and 95% CI, and population-attributable risks (PARs) were calculated for each measure overall and for each ethnic group by comparison of the top four quintiles with the lowest quintile. FINDINGS The apolipoprotein B100 (ApoB)/apolipoprotein A1 (ApoA1) ratio had the highest PAR (54%) and the highest OR with each 1 SD difference (1.59, 95% CI 1.53-1.64). The PAR for ratio of LDL cholesterol/HDL cholesterol was 37%. PAR for total cholesterol/HDL cholesterol was 32%, which was substantially lower than that of the ApoB/ApoA1 ratio (p<0.0001). These results were consistent in all ethnic groups, men and women, and for all ages. INTERPRETATION The non-fasting ApoB/ApoA1 ratio was superior to any of the cholesterol ratios for estimation of the risk of acute myocardial infarction in all ethnic groups, in both sexes, and at all ages, and it should be introduced into worldwide clinical practice.

Risk factors for myocardial infarction in women and men: insights from the INTERHEART study

AIMS Coronary heart disease (CHD) is a leading cause of death among men and women globally. Women develop CHD about 10 years later than men, yet the reasons for this are unclear. The purpose of this report is to determine if differences in risk factor distributions exist between women and men across various age categories to help explain why women develop acute MI later than men. METHODS AND RESULTS We used the INTERHEART global case-control study including 27 098 participants from 52 countries, 6787 of whom were women. The median age of first acute MI was higher in women than men (65 vs. 56 years; P < 0.0001). Nine modifiable risk factors were associated with MI in women and men. Hypertension [2.95(2.66 -3.28) vs. 2.32(2.16-2.48)], diabetes [4.26(3.68-4.94) vs. 2.67(2.43-2.94), physical activity [0.48(0.41-0.57) vs. 0.77(0.71-0.83)], and moderate alcohol use [0.41(0.34-0.50) vs. 0.88(0.82-0.94)] were more strongly associated with MI among women than men. The association of abnormal lipids, current smoking, abdominal obesity, high risk diet, and psychosocial stress factors with MI was similar in women and men. Risk factors associations were generally stronger among younger individuals compared to older women and men. The population attributable risk (PAR) of all nine risk factors exceeded 94%, and was similar among women and men (96 vs. 93%). Men were significantly more likely to suffer a MI prior to 60 years of age than were women, however, after adjusting for levels of risk factors, the sex difference in the probability of MI cases occurring before the age of 60 years was reduced by more than 80%. CONCLUSION Women experience their first acute MI on average 9 years later than men. Nine modifiable risk factors are significantly associated with acute MI in both men and women and explain greater than 90% of the PAR. The difference in age of first MI is largely explained by the higher risk factor levels at younger ages in men compared to women.

Risk Factors Associated With Myocardial Infarction in Africa The INTERHEART Africa Study

Background— Cardiovascular disease (CVD) is rising in low-income countries. However, the impact of modifiable CVD risk factors on myocardial infarction (MI) has not been studied in sub-Saharan Africa (SSA). Therefore, we conducted a case-control study among patients with acute MI (AMI) in SSA to explore its association with known CVD risk factors. Methods and Results— First-time AMI patients (n=578) were matched to 785 controls by age and sex in 9 SSA countries, with South Africa contributing ≈80% of the participants. The relationships between risk factors and AMI were investigated in the African population and in 3 ethnic subgroups (black, colored, and European/other Africans) and compared with those found in the overall INTERHEART study. Relationships between common CVD risk factors and AMI were found to be similar to those in the overall INTERHEART study. Modeling of 5 risk factors (smoking history, diabetes history, hypertension history, abdominal obesity, and ratio of apolipoprotein B to apolipoprotein A-1) provided a population attributable risk of 89.2% for AMI. The risk for AMI increased with higher income and education in the black African group in contrast to findings in the other African groups. A history of hypertension revealed higher MI risk in the black African group than in the overall INTERHEART group. Conclusions— Known CVD risk factors account for ≈90% of MI observed in African populations, which is consistent with the overall INTERHEART study. Contrasting gradients found in socioeconomic class, risk factor patterns, and AMI risk in the ethnic groups suggest that they are at different stages of the epidemiological transition.

Where does the black population of South Africa stand on the nutrition transition

OBJECTIVE To review data on selected risk factors related to the emergence of noncommunicable diseases (NCDs) in the black population of South Africa. METHODS Data from existing literature on South African blacks were reviewed with an emphasis placed on changes in diet and the emergence of obesity and related NCDs. DESIGN Review and analysis of secondary data over time relating to diet, physical activity and obesity and relevant to nutrition-related NCDs. SETTINGS Urban, peri-urban and rural areas of South Africa. National prevalence data are also included. SUBJECTS Black adults over the age of 15 years were examined. RESULTS Shifts in dietary intake, to a less prudent pattern, are occurring with apparent increasing momentum, particularly among blacks, who constitute three-quarters of the population. Data have shown that among urban blacks, fat intakes have increased from 16.4% to 26.2% of total energy (a relative increase of 59.7%), while carbohydrate intakes have decreased from 69.3% to 61.7% of total energy (a relative decrease of 10.9%) in the past 50 years. Shifts towards the Western diet are apparent among rural African dwellers as well. The South African Demographic and Health Survey conducted in 1998 revealed that 31.8% of African women (over the age of 15 years) were obese (body mass index (BMI) > or = 30kg m(-2)) and that a further 26.7% were overweight (BMI > or = 25 to <30 kg m(-2)). The obesity prevalence among men of the same age was 6.0%, with 19.4% being overweight. The national prevalence of hypertension in blacks was 24.4%, using the cut-off point of 140/90 mmHg. There are limited data on the populations physical activity patterns. However, the effects of the HIV/AIDS epidemic will become increasingly important. CONCLUSIONS The increasing emergence of NCDs in black South Africans, compounded by the HIV/AIDS pandemic, presents a complex picture for health workers and policy makers. Increasing emphasis needs to be placed on healthy lifestyles.

Hypertension in South African adults: results from the Demographic and Health Survey, 1998

Objectives To determine the prevalence and treatment status of hypertension in South Africa. Design National cross-sectional survey. Setting 13 802 randomly selected South Africans, 15 years and older, were visited in their homes in 1998. Methods Trained fieldworkers completed questionnaires on lifestyle and chronic diseases, measured blood pressure with an Omron manometer and recorded chronic drug utilization. Drugs were classified using the Anatomical Therapeutic Chemical index. Results The mean systolic blood pressure for men and women was 123 mmHg (SE 0.37) and 119 mmHg (SE 0.36), while the mean diastolic level was 76 mmHg (SE 0.25) and 75 mmHg (SE 0.20), respectively. When using a cut-off point of 140/90 mmHg the hypertension prevalence rate (age-adjusted to the South African Population, Census 1996) was 21% for both genders. Using the current cut-off point (160/95 mmHg) for South Africa, the prevalence rate was 11% for men and 14% for women. For men with hypertension, the level of awareness, taking antihypertensive medication and having controlled blood pressure (< 160/95 mmHg) were 41, 39 and 26% respectively, while for women these rates were 67, 55 and 38% respectively. Conclusions This survey revealed high levels of hypertension in the South African community with inadequate treatment status.

Prevalence of cardiovascular diseases and associated risk factors in a rural black population of South Africa

Background To determine the prevalence and associated risk factors of cardiovascular diseases in a rural adult black population from Limpopo Province in South Africa. Design A cross-sectional study. Methods A sample of 1608 women and 498 men aged 30 years and above participated in the study. Sociodemographic data, anthropometric measures (body mass index, waist/hip ratio), blood pressure and biochemical risk factors were measured. A global cardiovascular disease (CVD) risk profile was developed. Results There was a high prevalence of tobacco use for men (57%) and women (35.4%), with women (28.1%) predominantly using smokeless tobacco. Alcohol use was very common in men (57.2%). Women weighed a great deal more than men, and 51.7% were either overweight or obese. Diabetes was diagnosed in 8.8 and 8.5% of women and men, respectively. High-density lipoprotein-cholesterol was relatively high, whereas 42.3% of women and 28.5% of men had low-density lipoprotein-cholesterol levels of 3 mmol/l or more. Hypertension (blood pressure ≥ 140/90 mmHg) was found in 25.5% of women and 21.6% of men. According to the Framingham formulae, 18.9% of women and 32.1% of men had a 20% or higher chance of having a CVD event in the next 10 years. Conclusions There was a high prevalence of chronic disease risk factors in the rural, poor black community in Limpopo, South Africa. Consequently, the population had a higher than expected risk of developing a CVD event in the following 10 years when compared with similar studies in black Africans.

Cost-Effectiveness Analysis of Hypertension Guidelines in South Africa Absolute Risk Versus Blood Pressure Level

Background— Hypertension is responsible for more deaths worldwide than any other cardiovascular risk factor. Guidelines based on blood pressure level for initiation of treatment of hypertension may be too costly compared with an approach based on absolute cardiovascular disease (CVD) risk, especially in developing countries. Methods and Results— Using a Markov CVD model, we compared 6 strategies for initiation of drug treatment—2 different blood pressure levels (160/95 and 140/90 mm Hg) and 4 different levels of absolute CVD risk over 10 years (40%, 30%, 20%, and 15%)—with one of no treatment. We modeled a hypothetical cohort of all adults without CVD in South Africa, a multiethnic developing country, over 10 years. The incremental cost-effectiveness ratios for treating those with 10-year absolute risk for CVD >40%, 30%, 20%, and 15% were

Rising diabetes prevalence among urban-dwelling black South Africans.

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Chronic noncommunicable diseases and HIV-AIDS on a collision course: relevance for health care delivery, particularly in low-resource settings—insights from South Africa

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A comparative risk assessment for South Africa in 2000: Towards promoting health and preventing disease

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